1. Field of Invention
The present invention relates generally to methods for hydraulic infrastructures reinforcement and rehabilitation, and more particularly to a directional fracture grouting method with polymer for seepage control of dikes and dams.
2. Description of Related Arts
The safety of hydraulic infrastructures such as reservoirs is one of the top priority safety concerns. If a reservoir collapses, it could cause heavy damages to properties or even casualties. Seepage, a problem commonly associated with dams or dikes, is generally considered as a hidden danger. Many dam disasters were caused by the failure of their seepage control systems. Various solutions have been proposed. Among the available options, fracturing or splitting grouting is a commonly used method or technique.
The theory base for fracturing grouting is that the minimum principal stress plane is parallel or in the same direction as the axial direction of a dike or dam. Based on this theory and the principles of hydraulic fracturing, the technique of fracturing grouting comprises drilling holes along the axis of a dike or dam where the reinforcement mechanism is supposed to be installed. A grout composition is then injected into the holes. Under the hydraulic fracturing effect and the injecting pressure energy, the grout composition forces its way into hidden cracks, holes, fills up the voids and gets the soil compacted. As a result, it forms vertical, continuous, and impermeable barriers inside the dike or dam, thus achieving seepage control and dam reinforcement. Cement slurry is commonly used in the fracturing grouting technique, which has the following shortcomings:                (1) Grouting holes are typically large in size, which could undermine the safety or the structural soundness of the dike or dam;        (2) Grouting pressure is not easily controlled;        (3) Cement slurry may not be able to reach every crack or hole. It is especially so for the deeper areas where the slurry may not be able to be distributed effectively;        (4) For purpose of seepage control, a continuous curtain is required to form along the axial direction of the dike or dam, but it is hard to use the fracturing grouting technique to guide the cement flow to form a continuous curtain;        (5) Grouting process is time consuming and labor intensive;        (6) After the cement slurry sets, a rigid curtain is formed within the dike or dam. Deformation or cracking are likely to occur because the rigidness of the concrete wall is not good at adapting itself to the change or shift of the surrounding soil.        
It is clear that the existing fracturing grouting technique can't satisfactorily meet the requirements for seepage control of dikes and dams. Developing a better and more effective technique for seepage control for dikes and dams has become imperative.
Grouting with polymer, a technique developed since 1970s, allows rapid treatment for foundation repair. It has been used to reinforce foundations, fill up hollow spaces underground, or elevate floor by injecting two-component polymer materials into the foundation which then expands under chemical reaction and then coagulates. At present, grout polymer has been applied mostly in foundation repair or road maintenance. There is no report about techniques of directional fracture grouting with polymer for dikes and dams.